Transmitter output coupling circuit



y 1951/ o. l. STEIGERWALT 2,562,342

TRANSMITTER OUTPUT COUPLING CIRCUIT Filed Feb. 18, 1946 nvvz/vron. OLIVER L STEIGERWALT @MWQMY 53) I 54 "ATTORNEY Patented July 31, 1951 Y Q UNITED STATES PATENT orr cs TRANSMITTER OUTPUT COUPLING CIRCUIT Oliver Irsteigerwalt, Niagara Falls, N. Y., assignor to the United States of America as represented by the Secretary of War Application February 18, 1946, Serial No. 648,543

3 Claims. Cl. 250-36) This invention relates in general to electrical apparatus and more particularly to magnetron oscillators.

In the generation of ultra high frequency oscillations it is often convenient to use a magnetron oscillator to produce high frequency waves at relatively high power levels. Various types of magnetron tubes are in use at the present time, one of them being the split-anode transit-time type. magnetrons in common use the split-anode type requires an external plate tank circuit. At frequencies in the U.-H.-F. bands such a tank takes the form of a resonant parallel line. The line is tuned by moving some form of shorting means associated therewith in order to change the effective length of the wires forming the line. The general operation of a split-anode magnetron is clearly set forth in chapter of Ultra High Frequency Techniques, by J. G. Brainerd et al., D. Van Nostrand, Inc., New York, 1942, and will not be elaborated here.

Coupling from the tuned line to an output means is customarily done by inserting a probe into the field between the wires or by connecting a conductor directly to one of the wires. Since the coupling arrangement must lie between the magnetron and the shorting bar, it is clear that if the shorting bar is to be movedover any considerable range of positions, the coupling means will have to be repositioned to avoid interference with the motion of the shorting bar. In addi-- tion, if the degree of coupling is to be changed the coupling means must be adjusted independently of theshorting bar. If it is desired to retune the magnetron to a new frequency and retain the same degree of coupling, both shorting bar and coupling means must be moved.

Accordinglyit is one of the objects of my'invention' to provide a means for coupling to the tank circuit of a split-anode magnetron oscillator.

Another object is to provide proper coupling for maximum oscillator efiiciency over a relatively wide range of frequencies.

Still another object is to provide means for minimizing coupling adjustments with tuning changes.

Still another objectis to provide a simple tuning arrangement for a magnetron oscillator such In contrast to certain other varieties of of magnetron oscillator. The outer conductor of the line is not connected to the resonant circuit and gives an effect equivalent to that of an inductance in series with the output line. By means of this inductive effect the spacing between a frequency, while the degree of coupling remains unchanged. Means are provided for driving the shorting bar and simultaneously moving the member coupling to the tank circuit line. Means also are provided for moving the latter member independently of the aforesaid driving means.

The principles and operation of my invention will be more apparent to those skilled in the art upon reference to the following specification, claims, and to the drawings in which:

Fig. 1 is a perspective view of one embodiment of 'my invention; j

Fig. 2 shows an enlarged view of a portion of the apparatus of Fig. 1;

Fig. 3 is a view of a portion of the mechanical drive for the moving members; and, i

Fig. 4 is a schematic diagram of the essential elements of the apparatus in Fig. 1.

Reference is now made to Fig. 1 in which the relations of the various members of one embodiment of my invention with one another are shown in perspective. A split-anode magnetron tube 5 has connected to it two rod-like conducting members 6 and 1 forming the tank circuit for the tube. The magnetron envelope is supported by a rest 9 which is mounted in a box [0 a portion of which is broken away to show-its contents. The interior siirfaces of box 10 are covered with a conducting material so that the box forms an electrostatic and an electromagnetic shield for the electrical elements therein. Magnetic pole pieces I l are mounted on either side of the'magnetron tube 5 in well known fashion to provide the requisite magnetic flux.

1 A metallic plate l4 edged with spring fingers I5 is pierced to allow it to'be slipped over rods Band land yet maintain a sliding contact with the rods. Plate l4 provides a short circuit between rods 6 and 1 and comprises what has been referred to in general as a shorting ban.- Fingers I5 make contact with the conducting lining of box I0 thus tending to hold plate [4 in position and providing an electrical path between the plate and the box.

The output coaxial coupler is positioned between plate I4 and magnetron 5, centerconductor 18' terminating in a spring attachment l9 which makes sliding contact with rod 6. The coupler has a collar 20 furnished with spring fingers 2| which is slipped over outer conductor 22. The coaxial line passes through a slot 29 in the rear wall of box I and makes connection with output line 26 in such a fashion as to transfer power thereto regardless of the position of contacts I9 along the length of rod or=wire"6. Outer conductor 22 is electrically connected -to the conducting lining of box l0 through collar 20 and springs 2|.

A threaded shaft 25 may be seen through slot 29 and in practice has been positioned outside of box [0. This shaft engages with a carriage to which plate I 4 is mechanically connected iniorder that the operation of some external control such as handwheel 30 will cause the movement of .plate I4 along the axis of box [0. Blocks '32 and 33 which slide on guide rod 34 form a portion of the support and guiding means for this carriage.

Therehas been omitted from this view of my apparatus, for purposes of;ease of illustration and clarity, a second shaft and handwheel mechanism which servesto alter the spacing between the output coupler and the shorting plate, and 'which will be shown-in Fig.3.

Further details-;.of the-shortingplate and coupling apparatus-are shown in-Figs. 2 and 3. Fig. 2 is a top view showing-the manner in which the movable memberscomprising the coupling means and the shortin means inside box ID are brought through theaforementioned slot in the wall of the: box.;.A--member 36 attached to shorting -plate t4 passes through-the slot and is rigidly fastened to;- s horting .uplate carriage 31.

Outer conductor 22 of the-coaxial output line is connected to coupling block 38- and the members 31 and 38 aregshown more clearly in the showing ofFig. 3. I The member3-8 is constructed to form a link between the coaxial line connected to the tank circuit and transmission line 26 which car-.

ries power to an antenna or other load. Blocks 32 and33-andguiderod .34 cooperate to support and guide the shortingplate carriage and the coupling .block.

Fig. 3 shows in some detail one method of .driving shortin plate carriage 31 and coupling block 38. Tln'eadedrod 25 passes through both of these members but only the hole in carriage 31 is threaded to engage with the threads on the rod, the hole-in block 38 being bored large enough to allow free passage of the rod therethrough. -Rod-40 is not shown in Fig. 1 butis parallel to andsubstantially the same length as rod 25, terminating in a-handwheel or crank mechanism similar to that attached to rod 25. Rod 40 is unthreaded and-agroove or keyway 4| runs'the length of it. "Sleeve 42, the exterior of which is threaded, fits over rod 40 and key 4-3 joins the sleeve to the-rod so that the former is free to move'along the latter but rotationo'f the rod is followed by the 'sleeve. 'Sleeeve 42 isloosely attached' t'o' shorting plate carriage 31 'byimeans of collar '45 whichfits into a similarly shaped groove or'slot' in the carriage. Therefore the sleevecan'rotate freely with shaft 40 but is constrained to move longitudinally with the car'- riage. An additional guide rod 41 is'provided to support and direct carriage 31;

An inspection of Fig; 3 will show that revolution of rod"25 will produce'equal increments of longitudinal displacement in both carriage '31 and coupling block 38, while rotation of shaft 40 will produce longitudinal motion only incou- 4 pling block 38, thus achieving the desired motion of the shorting plate and output coupling line.

Referring to Fig. 4, there is shown a, schematic equivalent diagram of a split-anode magnetron, a resonant line tank, and a coaxial output means for explanatory purposes. In this figure dimension A represents the distance between shorting means 5 fl andmagnetronanode .5 I while dimension B is the distance 'b'et'ween shorting bar 50 and the output coupler attachment 52. Coil 53 represents the inductance offered by that section .of the outer conductor of the coaxial line 54 which projects into the box enclosing the oscillator. This-inductive eifect is due to cur- :rents' flowing over the outer surface of the outer conductor in the region inside the box or enclosure. Theamount of inductive effect can be adjusted by changing the shape of the portion of the output line outer conductor extending into the cavity of the bulk.

-Henoe itis possible to adjust dimensions A and B independently to a given value of frequency and optimum degree of couplin and then to alterboth dimensions by'equalincrements while retaining optimum coupling at any frequency. In this way-asingle-control may be used to make :adjustments'a'fter the'original settings combining convenience and speed of adjustment with maximum oscillator efllciency at all times.

While there has been described hereinabove whatis at present considered to be a preferred embodiment of the present-invention, it will be obvious to thoseskilled i'n-tlie art that changes and modifications maybe i made therein without exercise of inventive ingenuity. Hence, I claim all 'such modifications and adaptations as may fall fairly within thespirit'and scope of the hereinafter appended claims.

. What I'claimis:

1. =In an ultra high frequency oscillator a splitanodemagnetron-tubey-a section of parallel-wire transmission line, means "connecting said line section to the anode electrode of said magnetron tube, a box-like structure of conducting material enclosing said magnetron tube and-said section of tr'ansmission'lina a plate of conducting material :"positioned tra nsversely' to the longitudinal axis of-said line "section-and making electrical contact 'with'said line and said box-like structure, a coaxial output line positioned between said ma'gnetron tube and-said plate, the center conductor of said 'coaxial line making contact with'one of the conductors of'said parallel-wire line and the-outer conductor of' said coaxial line projecting intosaid box-like structure and making-electrical contact only with said box-like structure, means for'varying the'spacing between said conducting plate and said magnetron tube, and means'for simultaneously varying'the spacing between said conducting plate and the point of contact of said'coaxial output line with said parallel-wire line.

2. In an ultra high frequency oscillator an electron discharge device, a tuned parallel-wire tank circuit means for electrically connecting said'ele'ctrondischarge device and said-tank'circuit,'elect'rica1 shielding means substantially enclosing said tank circuit, andoutput coupling means comprising a coaxial transmission line, the inner conductor of which makes electrical contact with one of the conductors-of said tank circuit and the outer-conductorof which makes electrical contact withsaidshielding at its point of passage through said shielding, and projects ing said conductors, means for moving said wall 5 and said output coupling means in unison along the conductors of said tank circuit.

3. The apparatus defined in claim 2 further including means for altering the spacing between 6 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number said short-circuiting wall and said output cou- 1 2,505,251

Number Name Date Hansell Jan. 28, 1936 Buschbeck et al. Nov. 19, 1940 Lawrance July 23, 1946 Knol et al. Apr. 25, 1950 FOREIGN PATENTS Country Date Great Britain Sept. 22, 1938 

